Rails used in the construction of railroad track require heat treatment to withstand metallurgical failure in normal use. FIG. 1(a) and FIG. 1(b) illustrate a typical flat-bottom rail 90 comprising head 90a, web 90b and foot 90c. Heat treatment, or metallurgical hardening, is sometimes focused on the rail's head since the head is the region that makes contact with the wheels of rolling stock, while the web connects the head to the foot for distribution of the bearing load to sleepers, or ties, and the bed beneath the rails. FIG. 1(c) illustrates typical terminology that is used to describe approximate regions of the head. The crown, or running surface, is the region making contact with a wheel's rim, while the wheel's flanges generally make contact with one side surface of the head. Lower jaw regions define the region of the head that connects the head to web 90b. Modern railroad design can require relatively long lengths of a continuous rail, for example, in excess of 20 meters. Rails can be fabricated in a hot rolling mill that produces a hot length of rail by forging. Heat treatment of the rail can be accomplished immediately upon exit from the rolling mill by proper scaling of the rail and quenching, for example, with a fluid medium, such as air and/or water. Satisfactory heat treatment of the rail's head must be performed when the cross sectional temperature profile of the head is generally the same along the entire longitudinal length, Lr, of the head. One approach is to heat the entire length of rail (that is, the head, web and foot) to the same cross sectional temperature after the rail exits from the hot rolling mill. However such an approach wastes energy since web and foot cross sectional temperature uniformity is not required for effective heat treatment of the rail's head.
One object of the present invention is to provide apparatus for, and a method of, making the cross sectional temperature of a rail's head generally the same throughout the entire length of the rail by electric induction heating after the rail exits a hot rolling mill and before the rail is subjected to a quench process.